Phase Equilibria in Stimuli-responsive Gels: Theoretical Study of Smart PNiPAAm Gels in Organic Solvents

Abstract

Smart materials undergo significant configurational changes when exposed to certain stimuli. Therein, stimuli-responsive polymers and hydrogels are well-known materials, which show promising usability for the development of self-contained process control within the process unit geometries. Applicable stimuli types range from physical (temperature) to chemical (solvent composition) or biochemical (enzymes). Despite being versatile materials of major interest, smart gels have few actual application examples, due to missing insights into the thermodynamics of the response behavior. Many model approaches were developed improving this understanding. The difficulty in modeling the swelling behavior lies in the superposition of the equilibrium with the swelling kinetics. In this work, the behavior of stimuli-responsive gels in organic solvents is modeled using PC-SAFT and molecular dynamic simulations providing the possibilities of qualitative and quantitative description of swelling behavior. Comparing different solvents, the characteristics of different functional groups and their influence on the phase behavior are analyzed.